Conventionally, there is a phase control switching device that, when power is applied to a three-phase no-load transmission line, measures power supply voltages of the respective phases, detects power-supply-voltage zero points in each of the phases, and individually closes breakers for the respective phases near the detected power-supply-voltage zero points to thereby suppress generation of transient voltage and current (e.g., Patent Document 1).
Patent Document 1: Japanese Republication of PCT International Application WO00/004564 (pp. 28-29, FIGS. 1 and 3)